The invention relates to improvements in methods of an in apparatus for temporarily storing commodities and for removing, when necessary, commodities from storage. More particularly, the invention relates to improvements in methods of and in apparatus for removing (depalletizing) commodities from temporary storage facilities in the form of pallets. Typical examples of commodities which can be manipulated in accordance with the improved method and with or by the improved apparatus are stacks of superimposed articles, e.g., flat or substantially flat blanks of paper, cardboard, plastic material and/or metallic foil which are designed for conversion into containers or receptacles (such as packets) for arrays of plain or filter cigarettes or other articles or products of the tobacco processing industry. Still more particularly, the invention relates to improvements in methods of and in apparatus for depalletizing commodities which are temporarily deposited on normally at least slightly deformable and/or penetrable supports in the form of sheets, tarpaulins or panels which are placed between superimposed layers of commodities on pallets or analogous conveyances.
Depalletizing apparatus of the category of apparatus to which the present invention pertains are disclosed in European patents Nos. 0 532 949 A1, 0 363 722 B2 and 0 354 873 B1. The patented apparatus are designed to singularize accumulations of blanks which are stacked on pallets and are to be fed to packing machines, such as cigarette packing machines, for conversion into portions of or into entire packets, e.g., into packets each of which is dimensioned and configurated to accept and confine an array of twenty plain or filter cigarettes in the customary quincunx formation.
A modern high-speed cigarette packing machine (or another blank processing or converting machine) is designed to turn out huge quantities of packaged products per unit of time. Thus, even a relatively short interruption of the feed of blanks to such a machine can entail enormous losses in output. Therefore, such machines are often combined with a conveyor system which employs mobile pallets capable of temporarily storing numerous stacks of superimposed blanks, preferably in a distribution to afford convenient access to the stacks in a given sequence and unimpeded transfer into one or more blank-receiving magazines of a packing machine.
As mentioned above, it is already known to employ pallets which are designed to temporarily receive and transport large numbers of stacks of superimposed blanks made of paper, cardboard and/or other material or materials, often in the form of several superimposed layers which are separated from each other by sheet-like or analogous supports and each of which can contain a plurality (e.g., several dozens) of coplanar stacks. For example, the supports between neighboring superimposed layers of stacks of paper or cardboard blanks can be made of cardboard or a sheet- or panel-like material of similar consistency, and a pallet can support a substantial number of layers with supports (e.g., six cardboard panels) between neighboring layers.
Certain presently known depalletizing apparatus employ a tool or implement which is movable in several directions so that it can be caused to penetrate between the upper side of a topmost (or the only) support and the underside of a selected stack on such topmost or only support. The next step involves a lifting of the selected stack above and away from the upper side of the support and the transfer of the thus lifted stack onto a suitable conveyor which delivers the stacks into the blank-receiving magazine of a packing machine. As a rule, and in order to facilitate and simplify the introduction of the implement between the upper side of a support and the underside of a selected stack on such support, the implement is borne by a drive which can move the implement in the direction of the X, Y and Z axes, namely up and down (Z axis) as well as in a horizontal plane in two directions (X and Y axes) extending at right angles to each other. Once the implement has been moved to a required level (at the upper side of a support), it is moved in the direction of the X or Y axis to penetrate between the upper side of the support and the underside of the lowermost blank in a selected stack.
Problems arise when the upper side of a support is not smooth or is not flat or is slotted or otherwise damaged (e.g., as a result of repeated use) so that the normally sharp or reasonably sharp leading edge of the implement penetrates into and thereupon lifts a portion of the support together with a selected stack above it. This can result in undesirable shifting of one or more neighboring stacks on the partially lifted support and/or in at least some undesirable shifting (or complete collapse) of the stack overlying the implement. In either event, the transfer of stacks from the pallet must be interrupted for a certain interval of time to permit for manual separation of the implement from the lifted portion of the support as well as for the reestablishment of orderly distribution, orientation and configuration of neighboring stacks. This can entail huge losses in output, especially if the impaling and lifting of a portion of a support is detected with a certain delay. In many instances, an irregularity in the depalletizing operation can be remedied only upon stoppage of an entire production line, e.g., a production line embodying one or more cigarette rod makers, one or more filter tipping machines and one or more packing machines.